Robo-callers are a growing problem. For most, such robo-callers are an unwanted invasions of privacy. The United States Federal Trade Commission asked companies to rise to the challenge to stop such robo-callers; however, such an “ask” has largely resulted in no suitable technologies. Most blocking technologies simply use a global blacklist to prevent calls or just to identify a would be robo-caller on such a list. These blocking technologies miss the evolving numbers used by new robo-callers. They also can result in false positives, frustrating those who would seek to legitimately make a call.